Emerald Ash Borer (Agrilus Planipennis Fairmaire) (Coleoptera: Buprestidae)

THE USE OF CLASSICAL BIOLOGICAL CONTROL TO PRESERVE FORESTS IN NORTH AMERICA XVII Emerald Ash Borer (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae) Leah S. Bauer1, Jian J. Duan2, and Juli R. Gould3 1USDA Forest Service, Northern Research Station, East Lansing, Michigan, 48823, USA 2USDA Agriculture Research Service, Beneficial Insects Introduction Research Unit, Newark, Delaware, 19713, USA 3USDA APHIS PPQ, Center for Plant Health Science and Technology, Buzzards Bay, Massachusetts, 02542, USA In the Palearctic region, species in this genus are DESCRIPTION OF PEST grouped into 36 subgenera and 34 informal species-groups based on morphological characters of adults (Chamorro Taxonomy et al., 2012). On this basis, A. planipennis was placed in the Agrilus planipennis Fairmaire, 1888 (type locality: China) is subgenus Uragrilus Semenov (Alexeev, 1998). However, considered the senior synonym to A. marcopoli Obenberger, more recent analyses using adult and larval characters 1930 (type locality: China), A. marcopoli ulmi Kurosawa, 1956 suggest A. planipennis be moved to the Agrilus cyaneoniger (type locality: Japan), and A. feretrius Obenberger, 1936 (type species-group (Jendek and Grebennikov, 2011; Volkovitsh locality: Taiwan) by Jendek (1994) in a revision of Eastern and Hawkeswood, 1990). Palearctic Agrilus species. Agrilus is the largest genus in the family Buprestidae Distribution with ~2,800 described species worldwide (Bellamy, 2008). Countries in Asia where A. planipennis is reported include Adults of this genus are flashy, metallic-colored beetles, China, Korea, Russian Far East, Japan, Taiwan, Laos, and frequently collected using nets or traps (Fig. 1). However, Mongolia (Ko, 1969; Kurosawa et al., 1956, 1985; Chinese Academy of Science, 1986; Yu, 1992; Akiyama and Ohmomo, 1997; Mühle, 2003; Wei et al., 2004; Fukutomi and Hori, 2004; Jendek and Grebennikov, 2011). In areas of northeast China, Korea, and the Russian Far East, the distribution of A. planipennis generally coincides with that of ash trees (Fraxinus spp.) including F. chinensis Roxb., F. chinensis var. rhynchophylla, F. chinensis var. japonica, F. mandshurica Rupr., F. lanuginosa Koidz., and the introduced Nearctic species F. americana L., F. pennsylvanica Marsh., and F. velutina Torr. (Liu, Figure 1 Adult of emerald ash borer (Agrilus planipennis) on ash leaf. Leah Bauer, USDA Forest Service, North- 1966; Hou, 1993; Chinese Academy of Science, 1986; Yu, ern Research Station, East Lansing, Michigan. 1992; Zhang et al., 1995; Liu et al., 1996; Liu et al., 2003; there is little interest in their immature stages, which must be Duan et al., 2012a). However, in Japan, Taiwan, and Laos, collected from inside tree trunks, branches, or woody stems. confirmation that A. planipennis is native will require more Consequently, critical information on the biology, population information on species of Agrilus that feed exclusively on dynamics, and host ranges of most Agrilus species is lacking. Fraxinus spp. (Mühle, 2003; Bray et al., 2011). In Mongolia, 189 THE USE OF CLASSICAL BIOLOGICAL CONTROL TO PRESERVE FORESTS IN NORTH AMERICA the genus Fraxinus is unknown (Grubov, 1982), thus an America and Europe, respectively (Baranchikov, 2008; early, unconfirmed report of A. planipennis there is suspect Izhevskii et al., 2010). The expansion of EAB’s range to (Alexeev, 1979). the Western Palearctic region threatens European ash In 2002, A. planipennis was discovered in North species, including F. angustifolia Vahl., F. excelsior, and F. America after being reared from dead and dying ash trees ornus L. (Wessels-Berk and Scholte, 2008). The invasive from southeastern Michigan and nearby Ontario, Canada, population of EAB in North America only attacks (Haack et al., 2002). Due to the bright green coloration of A. Fraxinus spp. (Anulewicz et al., 2008), and several studies planipennis adults, this species was given the common name report that species of Nearctic and European ash are more of emerald ash borer (EAB) (Entsoc.org, 2012). In areas of attractive and susceptible to EAB attack than are species North America currently infested with EAB, its host range of Asian ash, which coevolved with EAB (Liu et al., 2003; and distribution (Fig. 2) coincides with that of Fraxinus). Rebek et al., 2008; Duan et al., 2012b). Figure 2 The known distribution and quarantines of emerald ash borer in North America as of June 1, 2012. Genetic studies of EAB from North America and Upon arrival in North America, EAB became Asia, and tree-ring analyses of ash trees in southeast established and spread throughout the Great Lakes Region, Michigan, indicate that this beetle was introduced from due in part to the abundance of ash trees in the urban and China during the 1990s (Siegert et al., 2009; Bray et al., forested landscapes (MacFarlane and Meyer, 2005; Poland 2011). The most likely route of entry was EAB-infested and McCullough, 2006; Pugh et al., 2011), limited EAB ash lumber used for the manufacture of crates, palettes, resistance to attack among native ash (Rebek et al., 2008), and dunnage used in international shipping. Within a and release from its native natural enemies (Bauer et al., few years of its detection, EAB was determined to be 2004, 2005; Duan et al., 2009). Although EAB adults are the cause of ash mortality in other nearby states and capable of long-distance flight (Taylor et al., 2010), much provinces (Fig. 2). of the spread of EAB in North America is facilitated In 2006, EAB was found in Moscow, Russia, where by human-assisted movement of infested ash firewood, it caused extensive mortality in urban plantings of F. nursery stock, and lumber (Cappaert et al., 2005; Poland pennsylvanica and F. excelsior L., ash species native to North and McCullough, 2006). In an effort to reduce the loss 190 EMERALD ASH BORER XVII THE USE OF CLASSICAL BIOLOGICAL CONTROL TO PRESERVE FORESTS IN NORTH AMERICA of North American ash trees, regulatory agencies in both the United States and Canada imposed quarantines on the movement of ash materials and attempted eradication of EAB by removal of the ash trees around known infestations. The eradication efforts ended when it was found that EAB was distributed across much of central and northeastern areas of North America. Infestations of EAB are now known in 22 states (Colorado, Connecticut, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Figure 3 Emerald ash borer eggs are white (left) when freshly laid, but turn tan as they age (right). David Cappaert, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Michigan State University, Bugwood.org. New Hampshire, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Wisconsin) and Ontario and Quebec, Canada (Fig. 2). Damage Type Emerald ash borer females lay their eggs (Fig. 3) singly or in small clusters between the layers of bark or in bark crevices of ash trees. Upon egg hatch, the neonates bore directly through the bark and into the tree until reaching the phloem and cambial region, where they feed (Cappaert et al., 2005). As larvae grow through four larval stages (Fig. 4), they leave behind increasingly large, frass- filled, serpentine galleries (Fig. 5). Larval feeding disrupts the transport of nutrients and water in the phloem and outer sapwood. At low EAB-larval densities, ash trees exhibit some immune response, notably the formation of callous around EAB galleries (Duan et al., 2012b). However, as larval densities increase over a period of two to five years, the phloem is consumed or sufficiently damaged to cause tree death (Figs. 6, 7) (Smith, 2006). Extent The establishment and spread of EAB in North America has resulted in the death of tens of Figure 4 Feeding stage larvae of emerald ash borer: above, millions of ash trees in urban and forested ecosystems. second, third and 4th instars; below, full-grown 4th in- star. David Cappaert, Michigan State University, Bug- In forested ecosystem of the eastern United States, there wood.org. are an estimated 8 billion ash trees valued at $US 282.25 billion (Federal Register, 2003; Nowak et al., 2003). Until at $US 11.7 billion (Federal Register, 2003; Kovacs et recently, ash trees were one of the most commonly planted al., 2010). The long-term ecological effects of EAB in landscape trees in the urban environment because they forested and riparian ecosystems are more difficult to grow rapidly, tolerate adverse growing conditions, are easy quantify (Federal Register, 2007). According to a recent to propagate, and were considered resistant to most pests. study, EAB has killed virtually the entire ash canopy of The costs for removal and replacement of ash trees killed southeast Michigan, and despite ash seedlings and saplings by EAB to communities and smaller landholders are high; in gaps, recovery of an ash overstory is unlikely due to the e.g., the expense for ash removal and replacement in six continued EAB infestation across the landscape (Kashian infested southeastern Michigan counties was estimated and Witter, 2011). Models of EAB spread predict a rapid XVII EMERALD ASH BORER 191 THE USE OF CLASSICAL BIOLOGICAL CONTROL TO PRESERVE FORESTS IN NORTH AMERICA Figure 5 Galleries caused by feeding emerald ash borer larvae. Left, Michigan Department of Agriculture, Bugwood.org. RIght, Edward Czerwinski, Ontario Ministry of Natural Resources, Bugwood.org. Figure 6 Dead and dying ash in forest area due to emerald ash borer. Troy Kimoto, Canadian Food Inspection Agency, Bugwood.org. 192 EMERALD ASH BORER XVII THE USE OF CLASSICAL BIOLOGICAL CONTROL TO PRESERVE FORESTS IN NORTH AMERICA Figure 7 Small trees with epicomic shoots due to the emerald ash borer. David Cappaert, Michigan State University, Bugwood.org. expansion of the infestation throughout North America layers of loose bark and in bark crevices. The eggs of (BenDor et al., 2006; Muirhead et al., 2006; Prasad et al., EAB are ca. 1.0 mm in diameter and amber in color when 2010; Mercader et al., 2011), and researchers are concerned mature.

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